I have seen skimmers and their piping destroyed by the long term practice of putting tablets in them. The baskets go rather quickly. If the pump is turned off you will develop a very high concentration of chlorine in a very small volume of water. It costs a lot of money to replace a skimmer.

The lowest setting of the Intelliflo may not be the most efficient so I would simple up the flow rate (RPM) until the SWG is happy.

The Intelliflo efficiency peaks at around 1000 RPM (i.e. highest gallons per watt-hour. Depending on your plumbing, that should be enough flow rate for the SWG.

Mas,
Typical engineer answer.
Read the question, there is not a SWG system, it is a in-line chlorine feeder.

Its funny you are posting this,
I recently finished a monster pool with two filtration systems, each with intelliflos', and two #320's. Pool cleaner just called me and says tabs are not erroding.
I will let you know what my solution is when I figure it out.

Mas,
I'll cut you some slack for not reading my post correctly! I'm sure that your answer would have been the same, however.

I've watched the YouTube video where the guy tests the pump flow/wattage at four levels and the numbers make it appear that slower is always better. Can you explain the forces at work that make the pump most optimal at 1000 RPM? Did you arrive at that by taking various flow/amp readings and looking for the sweet spot, or some other method? I would like to see a graph where the gallons per watt hour at the various settings were plotted out as I think that would be very interesting. Do you know where I could obtain those data points?

Also, wouldn't the optimal gallons/watt hour speed vary based on total head?

Thanks so much for your help in understanding.

Just-a-pb,

What speed were you running the pumps at when the 320's were not working? Let us know your solution.

djensen,

Sorry about misreading your post. My mistake. But your right, the answer doesn't really change much. My point is that the lowest setting is rarely the most optimal. You are also right in that the energy consumption changes as a function of plumbing head loss but what I have found is that the unsually falls within a small range around 1000 RPM. However, it still may not be enough in flow rate but it doesn't hurt to check. To me, this would be the simplest solution.

As to the efficiency of the pump, my comment was based upon several factors but mainly Pentair's own data, PG&E (power company) test data on pumps and reports from several owners. VF owners have been kind enough to give me a range of operating points which show flow rates, RPM and energy consumption.

I have been able to collect enough data to model the pump's behavior over a variety of operating conditions so I can fairly accurately predict the performance under almost any condition. Since there is a minimum amount of energy the pump consumes even at the lowest RPM setting due to the drive electronics, it really doesn't make sense to run it below about 800 RPM for most situations. The gallons pumped per watt-hour starts to fall below 900 RPM and above 1100 RPM for most plumbing systems.

The feedback from the VS-3050 is minimal so it is hard to tell what flow rate you have and how much energy is being consumed.

Do you have a flow meter installed? If not, there is a way to calibrate your system using filter pressure to determine flow rates and energy use. If you are interested, I can help you do that. Just post filter pressure at couple different RPM levels. If you can measure vacuum at the pump, all the better to increase accuracy.

Gorilla,

I saw the top feed option in the manual but it indicated that it was easy to over chlorinate with this setup. If you are running it wide open than you are apparently not finding that to be the case.

Mas,

It looks like you've really researched out the details on these. Thanks for being forthcoming with what you've learned.

I do have a traditional blue white flow meter that I could hook up but I could also measure the flow from one of the above water level ports with a bucket and a stopwatch.

So, let's accept that 1000 RPM is the optimal gallons per watt hour. This leads me the the following thought. It seems like keeping a pool clean is a function of the amount of water that you circulate through the filter and the amount of time that the water is actually circulating. My thought was that if you could run the pump for a much longer period of time, but at a very small level, you would keep the surface of the pool cleaner and keep the junk from settling to the bottom of the pool. So what do you think is more important? x turnovers per day regardless of how many or how few hours it takes to acheive that OR a constant skimming of the surface water for a longer period of time? If your answer is tilted toward time, than it could be conceivably more efficient to run at slower than optimal gallons per watt hour. What do you think?

djensen,

I was told by the PB guy that same thing: top feeds can over chlorinate. And from my experience, they do in Spa mode when I am pushing 90 GPM... so for spa mode, I have to set the dial to off. But as a top feed, one can always adjust the dial accordingly so that over-chlorination does not occur.

-Gorilla

djensen,

One of the problems people often find with the Intelliflo and very low speeds is that the skimming action is greatly diminished. The pool requires a minimum flow rate to get the water surface to move so that the skimmers can work. Overall, I think you are better off running at a slightly higher flow rate to get better efficiency, get your chlorinator to work and to get better skimming.

Also, measuring flow rates through external ports or even out of the returns leads to errors because the act of measurement will change the dynamic head of the pool which in turn changes the flow rate of the pump. The most accurate measurement is with a flow meter but only if you have a long piece of straight pipe that you can place it in. The second best method is with suction and pressure measurements at the pump. Filter pressure can be used as well.

Mas,

I was going to respond to you here but I thought it might be better to start another thread about a thought that I had related to this issue of running the pump for a long enough period of time to keep the surface debris flushed but keeping the Intelliflo at or about 1000 RPM. See you over at "Why not have multiple pump start/stop times"

I have the opposite problem. Low flow ( pump running 1500 to 2400) the pool gets too much chlorine. Any speed above, the 320 works great. Replaced the unit and same results